﻿using System;
using System.Collections.Generic;
using System.Web;
using System.Drawing;
using System.IO;

/// <summary>
///ThumbLogic 的摘要说明
/// </summary>
public class ThumbLogic
{
    /// <summary>
    /// 生成缩略图
    /// </summary>
    /// <param name="originalImagePath">源图路径（物理路径）</param>
    /// <param name="thumbnailPath">缩略图路径（物理路径）</param>
    /// <param name="width">缩略图宽度</param>
    /// <param name="height">缩略图高度</param>
    public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height)
    {
        MakeThumbnail( originalImagePath,  thumbnailPath,  width,  height, ThumbCutModes.Cut);
    }
    
    /// <summary>
    /// 生成缩略图
    /// </summary>
    /// <param name="originalImagePath">源图路径（物理路径）</param>
    /// <param name="thumbnailPath">缩略图路径（物理路径）</param>
    /// <param name="width">缩略图宽度</param>
    /// <param name="height">缩略图高度</param>
    /// <param name="mode">生成缩略图的方式</param>    
    public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, ThumbCutModes thumbCutMode)
    {
        Image originalImage = Image.FromFile(originalImagePath);
        MakeThumbnailDetail(originalImage,thumbnailPath, width, height, thumbCutMode);
    }


    /// <summary>
    /// 生成缩略图
    /// </summary>
    /// <param name="originalImageStream">源图路径的数据流</param>
    /// <param name="thumbnailPath">缩略图路径（物理路径）</param>
    /// <param name="width">缩略图宽度</param>
    /// <param name="height">缩略图高度</param>
    public static void MakeThumbnail(Stream originalImageStream, string thumbnailPath, int width, int height)
    {
        Image originalImage = Image.FromStream(originalImageStream);
        MakeThumbnailDetail(originalImage, thumbnailPath, width, height, ThumbCutModes.Cut);
    }

    /// <summary>
    /// 生成缩略图
    /// </summary>
    /// <param name="originalImageStream">源图路径的数据流</param>
    /// <param name="thumbnailPath">缩略图路径（物理路径）</param>
    /// <param name="width">缩略图宽度</param>
    /// <param name="height">缩略图高度</param>
    /// <param name="mode">生成缩略图的方式</param>    
    public static void MakeThumbnail(Stream originalImageStream, string thumbnailPath, int width, int height, ThumbCutModes thumbCutMode)
    {
        Image originalImage = Image.FromStream(originalImageStream);
        MakeThumbnailDetail(originalImage, thumbnailPath, width, height, thumbCutMode);
    }

    private static void MakeThumbnailDetail(Image originalImage,string thumbnailPath, int width, int height, ThumbCutModes thumbCutMode)
    {
        int towidth = width;
        int toheight = height;

        int x = 0;
        int y = 0;
        int ow = originalImage.Width;
        int oh = originalImage.Height;

        switch (thumbCutMode)
        {
            case ThumbCutModes.HW://指定高宽缩放（可能变形）                
                break;
            case ThumbCutModes.W://指定宽，高按比例                    
                toheight = originalImage.Height * width / originalImage.Width;
                break;
            case ThumbCutModes.H://指定高，宽按比例
                towidth = originalImage.Width * height / originalImage.Height;
                break;
            case ThumbCutModes.Cut://指定高宽裁减（不变形）    
            default:
                if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
                {
                    oh = originalImage.Height;
                    ow = originalImage.Height * towidth / toheight;
                    y = 0;
                    x = (originalImage.Width - ow) / 2;
                }
                else
                {
                    ow = originalImage.Width;
                    oh = originalImage.Width * height / towidth;
                    x = 0;
                    y = (originalImage.Height - oh) / 2;
                }
                break;
        }

        //新建一个bmp图片
        Image bitmap = new System.Drawing.Bitmap(towidth, toheight);

        //新建一个画板
        Graphics g = System.Drawing.Graphics.FromImage(bitmap);

        //设置高质量插值法
        g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

        //设置高质量,低速度呈现平滑程度
        g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

        //清空画布并以透明背景色填充
        g.Clear(Color.Transparent);

        //在指定位置并且按指定大小绘制原图片的指定部分
        g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight), new Rectangle(x, y, ow, oh), GraphicsUnit.Pixel);

        try
        {
            //以jpg格式保存缩略图
            bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
        }
        catch (System.Exception e)
        {
            throw e;
        }
        finally
        {
            originalImage.Dispose();
            bitmap.Dispose();
            g.Dispose();
        }
    }


}

public enum ThumbCutModes
{
    HW,//指定高宽缩放（可能变形）  
    W,//指定宽，高按比例 
    H,//指定高，宽按比例
    Cut,//指定高宽裁减（不变形）       
}
